The invention concerns an equipment for replacing a doctor blade, a doctor blade, and a method in the use of a band-like doctor blade.
For example, from the patent publications FI 54,076 and U.S. Pat. No. 4,691,406, the use of a band-like doctor blade material is known for servicing of roll faces. Thus, it is known to transfer a used doctor blade onto a winder for the used blade, and the unused doctor blade is fed from its own reel. The prior-art equipments are mainly hydraulic, and in their case oscillation of a doctor blade has also been permitted.
In the prior art devices, however, it is a particular drawback that the contact between the doctor blade and the roll is not fully adequate, because at the edges of the holder the doctor blade is bent in an uncontrolled way, and in such a case the wear of the doctor blade is also uncontrolled, which has the further consequence that the operation of the doctor blade in the prior-art solutions is not sufficiently reliable.
In the present patent application, it is suggested that such an equipment for replacing a doctor blade is used in which the doctor blade is passed from a reel of doctor blades, preferably from a storage box for doctor blades. Thus, at one end of the roll, the equipment comprises a blade feed device, and at the opposite end of the roll a blade pulling device. Both of said devices are operated when a blade is fed from a reel of doctor blades into connection with the roll. The doctor blade is passed into a blade opening of a blade holder for a conventional doctor blade, which holder is provided on a frame beam, and the blade is locked in its position in the blade opening by means of loading hoses which operate as a blade positioning device and, at the same time, as locking means.
In accordance with the present invention, it is an essential feature of the equipment for replacing a doctor blade and of the doctor blade and of the method in the use of the doctor blade in accordance with the present invention that the doctor blade is provided with edge notches at one longitudinal edge of the doctor blade. During operation of the doctor, said notches are placed at both ends of the area of use proper of the doctor blade. The notches permit controlled and uniform bending of the doctor blade during operation. In such a case, the blade is worn uniformly. When it is desirable to change the area of operation of said doctor blade, doctor blade is fed from the reel of doctor blades so that the edge notch at the outlet side of the doctor blade is placed at the end of the area of operation on the doctor blade holder, and the new edge notch is transferred in such a way into connection with the blade that it is placed at the inlet end of the doctor blade holder, as viewed in the feed direction L1. Thus, the doctor blade is fed periodically always over the length of one distance E1 between notches.
From the blade pulling device the used doctor blade is fed further to the winding device for used blade.
The blade solution in accordance with the invention mentioned above makes it possible to provide an equipment of an entirely novel type for replacing a doctor blade. In accordance with the invention, a band-like doctor blade can be fed directly out of a storage package for doctor blades from a reel, and said feed is carried out periodically always over the length of one distance E1 between notches. Thus, a blade in accordance with the invention is provided with notches at the side or edge, which notches permit satisfactory operation of the blade in accordance with the invention. In accordance with the invention, it is possible to use existing frame beams and doctor blade holders of a doctor equipment. In such a case, the blade is fed through the blade opening on the holder, at which time the blade loading members have been released. As the loading means, it is possible to use ordinary pneumatic hoses or equivalent. Also, other loading means can be used in order to lock the doctor blade in its holder.
The equipment for replacing a doctor blade, the doctor blade, and the method in the use of a band-like doctor blade in accordance with the invention are characterized in what is stated in the patent claims.